1. Field of the Invention
The present invention relates to a method of producing electrical energy from the rotary motion of the axles of vehicles, particularly of vehicles which travel on rails. The method utilizes a generator arrangement in which, in addition to producing electrical energy, the rate of rotation of the respective axle is determined.
The invention also relates to an axle generator arrangement, particularly for carrying out the above-described method. In particular, the arrangement includes a rotor which is coupled to the axle of the vehicle and is provided with permanent magnets which are arranged distributed over the circumference. The arrangement further includes a stator which is provided with induction coils and is spaced from the rotor through an air gap. The arrangement further has an electronic unit for evaluating the generator functions.
The invention further relates to the use of the above-described axle generator arrangement in the above-described method.
2. Description of the Related Art
German patent 25 51 009 discloses an alternating current generator to be mounted in an axle-bearing cover of a railroad car. It is known from this patent to mount within the alternating current generator a digital angle-of-rotation pick-up which is capable of determining the rate of rotation of the axle of the railroad car connected to the rotor of the generator. This known arrangement has the disadvantage that an additional rate-of-rotation pick-up is required for determining the rate of rotation of the axle. This arrangement increases the structural requirements in manufacturing such a generator. In addition, the additional pick-up requires maintenance. The rotor of this known alternating current generator is rigidly connected to the axle of the vehicle and is provided with permanent magnets whose flux lines emerge in the direction of the stator in axial direction. Consequently, located axially opposite the rotor is a stator with an appropriate arrangement of induction coils and ferrite cores. The axially oppositely located stator and rotor are spaced apart from each other by a defined air gap. As a result, the electrical energy which is generated depends in any situation of operation on the size of the air gap between rotor and stator and, thus, from the axial position of the vehicle axle. Since axial displacements of the axle certainly occur during operation, for example, when the vehicle travels through curves at high speed, the resulting changes in the air gap inevitably have a disadvantageous influence on the continuity and the constancy of the energy production. It is apparent that such an axial displacement is even inevitable because of the fact that the rotor must be coupled to the axle and rotates together with the axle and that the stator must be kept stationary, which is achieved, for example, by a rigid connection with the axle bearing support.
In the known generator, the disadvantageous effect of axial displacements of the axle are due to the fact that displacements in the range of millimeters already create a significant change of the air gap and, thus, of the electrical energy which is generated. When the electrical energy is used in sensitive measuring systems or control systems within the railroad vehicle, the resulting voltage fluctuations of the electrical energy are a disadvantage because an essentially voltage-constant electrical energy source must be available for an operationally safe supply of such a controlled arrangement. As a rule, an accumulator is provided as a "buffer" between the energy source or the "producer" and the "user." However, permanent fluctuations of the electrical voltage are also a disadvantage in this situation. In the event that the energy supply of important elements must be ensured during the travel operation for safety reasons when the accumulator fails or breaks down, an electrical energy source with substantial voltage fluctuation constitutes a great disadvantage, and even a dangerous disadvantage. Since different voltage values result in dependence on the speed, while the voltage must be maintained constant through an electronic unit, the compensation of the above-described additional voltage fluctuation would require an additional electronic unit.
The arrangement of a separate digital rate-of-rotation pick-up within the generator as described above with respect to the state of the art causes the functions of energy production and rate-of-rotation pick-up to be uncoupled and makes the system more susceptible to trouble.